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Robot may monitor nuke plants

A spherical robot equipped with a camera may navigate underground pipes of a nuclear reactor by propelling itself with an internal network of valves and pumps
A spherical robot equipped with a camera may navigate underground pipes of a nuclear reactor by propelling itself with an internal network of valves and pumpsHarry Asada / d'Arbeloff Laboratory

A cannonball-shaped robot with no outwardly visible means to move around could soon work its way into the piping systems of aging nuclear power plants to look for signs of rust, corrosion, and unwanted gunk that could cause a leak and contaminate groundwater.

The need for some type of inspector for these power plants was highlighted in June in a special report by the Associated Press, which found tritium, a radioactive form of hydrogen, has leaked from at least 48 of 65 commercial nuclear sites.

These leaks are raising doubts among independent engineers about the reliability of emergency safety systems at these sites because some of the pipes carry water meant to cool a reactor in an emergency shutdown to prevent a meltdown, the AP reported.

"You got pipes that have been buried underground for 30 or 40 years, and they've never been inspected, and the NRC (Nuclear Regulatory Commission)  is looking the other way," engineer Paul Blanch, who has worked for the industry and later became a whistleblower, told the news service. "They could have corrosion all over the place."

The spherical robots could be sent in to do these inspections, according to Harry Asada, a mechanical engineer at the Massachusetts Institute of Technology who is heading up the robot's design.

Instead of propellers, fins, or rudders, the robot moves with a specially designed system of Y-shaped valves embedded inside the sphere that harnesses the force of water moving through the reactor pipes, Asada and his team explain.

Depending on what direction operators want the robot to swim, they can close off various channels to shoot water through a specific valve. The high-pressure water pushes open a window at the end of the valve, rushing out of the robot and creating a jet stream that propels the robot in the opposite direction.

The design eliminates the need for external appendages that could snag on something as the robot maneuvers through the network or pipes, joints, and sensors, forcing a plant shut down and rescue mission, Asada said in a news release.

As the robot navigates the pipes, an onboard camera takes images. The plan is to beam the imagery to operators in real time with wireless underwater communications using laser optics. A hamster-ball like mechanism will allow the camera to pan and tilt in place by shifting its center of mass.

Asada envisions the robots as short-term, disposable patrollers with a lifetime of perhaps a few missions into a labyrinthine network before breaking down due to radiation exposure. A prototype was presented earlier this year at the IEEE International Conference on Robotics and Automation.

In addition to the AP report, ensuring the safety of nuclear power plants was demonstrated at the Fukushima Daiichi plant in Japan, which was damaged by an earthquake and tsunami last March; three of the six reactors suffered meltdowns.

To help deal with the crisis in Japan, iRobot deployed its Packbot to the damaged plant. Wilson Rothman reports on this robot deployment in the video below.

 More on nuclear power plants and robots:

John Roach is a contributing writer for